KA24(e) Throttle Body Modification

Short Explanation

Total cost of this mod: ~$50 for the TB, $2 for the gasket, and ~$10 in misc. tools if you don't already have them.

What this mod does? The TB on Nissan cars with the KA24(e) engine (2.4 Liter, 4 Cylinder, DOHC) has a direct bolt-on replacement TB for the stock Z31 TB. Two manufacturer's produced TB's for this engine: Nissan and Hitachi. The Hitachi required some modifications itself...you must replace its linkage (where the cable hook up) with what you already have on the stock TB. The Hitachi linkage only allows about 30 degrees of opening and you need a full 90. You also have to adjust the coolant lines and use a "T" to join two vacuum lines into one. If you're lucky enough to find a Nissan TB you should be able to take of the old and bolt on the new, as the linkage is the same. You can find the KA24(e) engine on 89-91 240SX, Stanza, and pickups. The 240SX's I've seen have never had the Nissan TB...only the Htachi. Stanzas I've seen do have the Nissan, and not the Hitachi. I never saw a truck to see what they sported...but if its a rear wheel drive (like the 240SX) I'd assume it also has the Hitachi.

Gains occur because the TB on the KA24(e) engines have an outlet diameter 10mm larger than on the Z. Both TB's (stock and KA24(e)) have the same size inlet, but the larger outlet allow more air to be sucked in on throttle. The AirFlowMeter and computer compensate for the higher flow of air with more fuel. More air/fuel mixture = more explosion = more HP. This won't give you gains like a turbo. The extra "boost" is small, but it is there. You will get better throttle response and a bit more kick outta your engine. Good mod and worth it.

Labor time depends on your approach. You HAVE to match port the intake collector for this mod to do you any good. The intake collector inlet is ALREADY bigger than the stock Z outlet by about 5-6mm...so you only need to port it out 4-5 mm more (by diameter...not on all sides [radius]). I suggest removing the intake collector to port match. Though it takes a long time, I wouldn't chance getting metal scraps down into your manifold and then down the intake valves into the cylinders. Some say stuffing a towel inside really tight is suffiecient, but I wouldn't chance it. Pull it off, stuff a towel down there, and then thoroughly wash it out before sticking it back on. I also took advantage when I had the intake collector off to paint my driver's side valve cover to match the rest of my newly painted engine parts.

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